A flip chip assembly uses a process in which the semiconductor die is assembled face down onto a substrate. To electrically connect the die to the substrate, a redistribution layer (RDL) is formed over the top metal layer of the semiconductor die to interconnect the die input/output (I/O) circuitry located at the periphery, to Under Ball Metallization (UBM) which may be located anywhere on the surface of the die. Conductive bumps connect the UBM to the substrate.
Conventional flip chip assemblies distribute power and ground from the I/O to the circuits of the semiconductor die. Relatively high voltage drops and power losses can occur in distributing power and ground, due to the distance from the I/O to the circuits and the magnitude of the currents. To reduce the voltage drops and power losses some flip chip assemblies locate the power and ground I/O towards the center of the die. Although relocating the power and ground I/O decreases the voltage drops and power losses, the relocated power and ground I/O may crowd out UBM from the core area of the semiconductor die. Since electrostatic discharge (ESD) structures are typically co-located with the power and ground UBMs, the problem with crowding out in the core area is exacerbated.